Infrared (IR) thermal imagers used by military and law enforcement personnel allow the detection of radiation emitted by people and objects. These devices image thermal radiation, typically manifested as long wavelength infrared (LWIR) light in the 8-12 μm wavelength range, emitted from objects in a scene to create a visual thermal representation of that scene. Objects and backgrounds which are warm and/or have a high emissivity radiate more thermal energy than comparable cold and/or low emissivity objects and backgrounds, and when the differences in radiated thermal energy across a scene is imaged, an operator can passively gain significant information about the objects in the scene without the need for active or environmental illumination. Additionally, IR thermal imagers allow for the collection of information which might be unobtainable or difficult to obtain through other methods. For example, the user of a thermal imager might observe a car sized cold spot on otherwise warm pavement providing evidence that a car had recently been parked at that location shading that area from sunlight. No other general use, field deployable device would provide that type of information as quickly and conclusively as a thermal imager. Another advantage of infrared imagers is that they are less attenuated by smoke and dust. These devices may be monoculars, binoculars, bioculars and goggles; and may be hand-held, weapon mounted, vehicle mounted, tripod mounted or helmet mounted.
These devices may employ an uncooled microbolometer focal plane comprised of a two-dimensional array of detector elements sensitive to LWIR radiation that translates energy from the radiation into electric impulses that are communicated to signal processing electronics and translated into data for viewing on a display by an operator. Other sensor/detector technologies exist including cooled LWIR focal plan arrays, mid-wave infrared (MWIR) focal plane arrays, single axis scanning mirror systems with a linear bar thermal detector, and dual axis scanning mirror systems with a point thermal detector.